Curved-IDT Acoustic Wave Filter for Lower Multiplexer Insertion Loss
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Solution Overview
Problem
Unwanted waves generated in acoustic wave resonators connected to a common terminal in multiplexers, such as quadplexers, affect the filter characteristics of other filters, leading to increased insertion loss.
Innovation Solution
Incorporating excitation angle change resonators with curved electrode fingers and non-uniform excitation angles in series and parallel arm resonators, reducing the influence of unwanted waves by altering the acoustic wave propagation direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple filters are connected in common to a terminal in a multiplexer, then the device can handle multiple communication bands, but unwanted waves generated in resonators affect filter characteristics of other filters leading to increased insertion loss
Solution Approach 1:
The patent applies local quality by making the excitation angle non-uniform only in specific resonators (front half resonators) rather than all resonators. The excitation angle varies across the electrode finger width in these specific resonators to suppress unwanted waves, while other resonators maintain uniform excitation angles for optimal filter performance.
Solution Approach 2:
The patent changes the excitation angle parameter in the IDT electrode design. By making the excitation angle non-uniform across the electrode finger width in specific resonators, the acoustic wave propagation characteristics are modified to suppress unwanted waves while maintaining the desired filter response.
2Device complexity
If uniform excitation angles are used in all resonators, then filter design is simplified, but unwanted waves cannot be suppressed effectively
Solution Approach 1:
The patent applies local quality by making the excitation angle non-uniform only in specific resonators (front half resonators) rather than all resonators. The excitation angle varies across the electrode finger width in these specific resonators to suppress unwanted waves, while other resonators maintain uniform excitation angles for optimal filter performance.
Solution Approach 2:
The patent applies partial action by implementing the non-uniform excitation angle design in only half of the resonators (front half resonators) rather than all resonators. This partial application is sufficient to suppress unwanted waves while maintaining overall filter performance and reducing design complexity compared to modifying all resonators.
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
Reduces the impact of unwanted waves, thereby minimizing insertion loss and improving filter performance in multiplexers.
Implementation Method 1
an interdigital transducer (IDT) electrode including a plurality of electrode fingers provided on the piezoelectric substrate
Implementation Method 2
The plurality of electrode fingers are curved. An excitation direction of an acoustic wave in a portion of an electrode finger in the plurality of electrode fingers
Data Source
AI summary
A filter device includes a first signal terminal, a second signal terminal, and a plurality of resonators including a plurality of series arm resonators and a plurality of parallel arm resonators. At least one of the plurality of series arm resonators and the plurality of parallel arm resonators is an excitation angle change resonator. The excitation angle change resonator includes a piezoelectric substrate including a piezoelectric body layer, and an IDT electrode including a plurality of electrode fingers provided on the piezoelectric substrate. The piezoelectric body layer has a propagation axis. The plurality of electrode fingers are curved. An excitation direction of an acoustic wave in a portion of an electrode finger in the plurality of electrode fingers is one of first to third directions.