Parallel Capacitor Acoustic Resonator for Narrowband Coupling Control
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Solution Overview
Problem
Current acoustic resonators have excessive coupling for narrow frequency bands, such as n79, making it challenging to design effective RF filters that can operate efficiently at these bands.
Innovation Solution
The proposed solution involves coupling a capacitor in parallel with an acoustic resonator to decrease the effective coupling by shifting the anti-resonance frequency lower, thereby improving the resonator's performance at narrow frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current acoustic resonators are used, then they provide sufficient coupling for wide frequency bands, but they have excessive coupling for narrow frequency bands such as n79
Solution Approach 1:
The resonator structure is segmented into multiple functional layers (piezoelectric layer, electrode layers, dielectric layers) that can be independently designed and optimized. The IDT fingers are segmented into multiple sets with different orientations to create distinct coupling paths, allowing precise control over the coupling coefficient for different frequency bands.
Solution Approach 2:
The patent employs parameter changes by varying the orientation angles of different IDT finger sets (e.g., 0 degrees, 60 degrees, 120 degrees) and adjusting their respective widths and spacing. These parameter modifications enable tuning of the coupling coefficient to achieve optimal performance for narrow frequency bands like n79 while maintaining versatility across wider bands.
2Adaptability or versatility
If coupling is increased for wide frequency bands, then wide band operation is achieved, but coupling becomes excessive for narrow frequency bands
Solution Approach 1:
Different regions of the resonator structure are assigned different local qualities through the use of IDT finger sets with specific orientations and dimensions. Each finger set contributes differently to the coupling characteristics, allowing the overall structure to provide both wide band coverage and reliable narrow band performance by combining localized functional advantages.
Solution Approach 2:
The resonator employs a composite structure combining multiple IDT finger sets with different orientations and characteristics on the same piezoelectric substrate. This composite approach allows the device to exhibit both strong coupling for wide band operation and controlled coupling for narrow band reliability, achieving dual functionality through structural composition.
3Manufacturing precision
If complex manufacturing processes are used to achieve precise coupling control, then narrow band performance improves, but manufacturing complexity increases
Solution Approach 1:
The resonator structure is designed with multi-functionality where the same basic IDT fabrication process can produce finger sets with different orientations and characteristics by simply changing lithography patterns. This universal approach allows precise coupling control for narrow bands without requiring entirely different manufacturing processes, reducing overall complexity.
Solution Approach 2:
The piezoelectric layer and electrode structures are prepared in advance with predetermined orientations and configurations before final assembly. This preliminary action allows the coupling characteristics to be pre-engineered into the structure, simplifying the final manufacturing steps while achieving precise coupling control for narrow frequency bands.
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 the coupling coefficient, allowing the resonator to operate more efficiently at narrow frequency bands, such as n79, while also simplifying the manufacturing process for such filters.
Implementation Method 1
a piezoelectric layer coupled to the substrate by one or more dielectric layers and having first and second surfaces that oppose each other; an interdigital transducer (IDT) on at least one of the first and second surfaces of the piezoelectric layer
Implementation Method 2
a capacitor electrically coupled in parallel to the IDT and including at least one first electrode on the first surface of the piezoelectric layer and a metal layer on the second surface of the piezoelectric layer
Data Source
AI summary
An acoustic resonator is provided that includes a substrate; a piezoelectric layer coupled to the substrate by one or more dielectric layers and having first and second surfaces that oppose each other; an interdigital transducer on at least one of the first and second surfaces of the piezoelectric layer and including interleaved fingers; and a capacitor electrically coupled in parallel to the interdigital transducer and including at least one first electrode on the first surface of the piezoelectric layer and a metal layer on the second surface of the piezoelectric layer, such that the piezoelectric layer is sandwiched between the at least one first electrode and the metal layer.