Acoustic Wave Element Outer Region Electrode Pitch
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Solution Overview
Problem
Existing acoustic wave duplexers in communication devices face challenges in improving the characteristic features of the passband for both reception and transmission bands.
Innovation Solution
An acoustic wave element with a piezoelectric substrate and an excitation electrode, featuring reflectors with modified electrode finger designs in the outer regions to adjust the resonant frequency and reduce spurious responses, is integrated into the duplexer, enhancing the passband characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave elements with uniform electrode finger design are used, then the structure is simple and easy to manufacture, but the passband characteristics and spurious response suppression are insufficient
Solution Approach 1:
The patent applies local quality by dividing the excitation electrode into a main region with uniform electrode fingers and outer regions with modified electrode finger designs. The outer regions have altered pitch or width parameters specifically at the end parts to suppress spurious responses, while the main region maintains uniform design for simplicity. This localized modification improves passband characteristics without making the entire structure complex.
Solution Approach 2:
The excitation electrode is segmented into functionally distinct regions: a main region with uniform electrode fingers for basic operation and outer regions with modified electrode fingers for spurious response suppression. This segmentation allows each region to be optimized for its specific function, improving overall device performance while maintaining manufacturing feasibility.
2Reliability
If the resonant frequency of reflectors is increased to improve filtering, then the passband characteristics improve, but acoustic wave leakage increases and loss rises
Solution Approach 1:
The patent changes the resonant frequency parameter of the reflectors to be lower than that of the main region electrode fingers. This parameter adjustment optimizes the balance between filtering performance and acoustic wave containment, reducing leakage and energy loss while maintaining effective signal filtering in the passband.
3Ease of manufacture
If uniform electrode finger design is used throughout the excitation electrode, then manufacturing is simplified, but spurious responses cannot be effectively suppressed
Solution Approach 1:
The patent implements local quality by maintaining uniform electrode finger design in the main region for ease of manufacture, while applying modified designs only in the outer regions at the end parts. This localized approach suppresses spurious responses generated at the boundaries without complicating the fabrication of the entire electrode structure.
Solution Approach 2:
Instead of modifying the entire excitation electrode, the patent applies partial modification only to the outer regions where spurious responses originate. This partial action is sufficient to suppress harmful effects while minimizing the complexity introduced to the overall manufacturing process.
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 effectively improves the passband characteristics by reducing spurious responses and preventing acoustic wave leakage, leading to better filter performance and reduced loss in communication devices.
Implementation Method 1
The acoustic wave element utilizes the characteristic feature that an electrical signal and a surface acoustic wave can be converted to each other by the relationship between the excitation electrode and the piezoelectric substrate
Implementation Method 2
In the reflector, a resonant frequency, which is determined according to the electrode finger design of the reflector electrode fingers, becomes lower than the resonant frequency determined according to the electrode finger design of the electrode fingers of the main region in the excitation electrode
Data Source
AI summary
An elastic wave element has a piezoelectric substrate; an excitation electrode which is located on an upper surface of the piezoelectric substrate and generates an acoustic wave, and two reflectors which are located on the upper surface of the piezoelectric substrate and sandwich the excitation electrode in the propagation direction of the acoustic wave. The excitation electrode has a main region located between the two end parts of the propagation direction and outer regions located on two sides of the main region. When the number of the electrode fingers of the outer region is “m”, an electrode finger interval of the main region is “a”, and an interval between the electrode finger of the main region on the outer region side and the reflector electrode finger of the reflector is “x”, 0.5×a×(m+1)<x<a×(m+1) is satisfied. Further, a resonant frequency of the reflector is lower than a resonant frequency in the main region of the excitation electrode.