Laterally Coupled BAW Resonators for Higher Q and Power Handling
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Solution Overview
Problem
Conventional Bulk Acoustic Wave (BAW) resonators suffer from lateral modes that degrade the quality factor Q and reduce power handling due to energy loss and coupling to unwanted Rayleigh-Lamb waves, which are not confined to the piezoelectric layer and escape the resonant cavity.
Innovation Solution
The BAW device employs an acoustic coupling structure between adjacent resonators to utilize lateral traveling waves for synchronized operation, enhancing power handling by engineering the coupling strength and synchronicity of BAW resonators through a mechanically and acoustically coupled system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional BAW resonators are used with thin piezoelectric layers and reflective elements, then the device structure is simple and easy to manufacture, but lateral Rayleigh-Lamb modes are triggered that escape the resonant cavity, causing energy loss and reducing the quality factor Q
Solution Approach 1:
The patent converts the harmful lateral Rayleigh-Lamb modes into beneficial acoustic coupling mechanisms. By intentionally designing acoustic coupling structures that utilize lateral wave propagation, the previously harmful energy loss pathways are transformed into controlled coupling channels between adjacent resonators, enabling synchronized operation and improved power handling while maintaining manufacturing simplicity
Solution Approach 2:
The patent introduces acoustic coupling structures as intermediary elements between adjacent BAW resonators. These structures mediate the interaction between resonators by controlling lateral wave propagation, enabling mechanical and acoustic coupling that synchronizes resonator operation and improves overall device performance without requiring fundamental changes to the basic resonator structure
2Device complexity
If lateral modes are allowed to propagate freely in conventional BAW resonators, then the device complexity remains low, but energy is lost through cavity escape, reducing power handling capability
Solution Approach 1:
The patent transforms the previously harmful lateral mode energy loss into a beneficial coupling mechanism. By designing acoustic coupling structures that guide lateral wave propagation, the energy that would otherwise escape and reduce power handling is now utilized to create synchronized mechanical coupling between resonators, enhancing power handling capability while maintaining low device complexity
Solution Approach 2:
The patent introduces dynamic coupling between resonators through acoustic coupling structures. The coupling strength and synchronicity are engineered to be可调 (adjustable) through the design of the coupling structures, allowing the system to adaptively optimize power handling performance based on operating conditions while maintaining structural simplicity
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 acoustic coupling structure improves power handling by ensuring in-phase current generation across the coupled system, thereby increasing the quality factor Q and reducing energy loss.
Implementation Method 1
a piezoelectric layer configured to propagate a BAW; a first bottom electrode and a second bottom electrode provided beneath the piezoelectric layer, respectively; a first top electrode and a second top electrode provided on the piezoelectric layer, respectively, wherein the first top electrode and the first bottom electrode sandwich the piezoelectric layer
Implementation Method 2
an acoustic coupling structure arranged between the first top electrode and the second top electrode on the piezoelectric layer, wherein the acoustic coupling structure is configured to allow an acoustic wave to propagate from the first resonator region into the second resonator region through the acoustic coupling structure
Implementation Method 3
The acoustic coupling structure improves power handling by ensuring in-phase current generation across the coupled system, thereby increasing the quality factor Q and reducing energy loss
Data Source
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AI summary
The present invention relates to acoustic wave devices, in particular to Bulk Acoustic Wave (BAW) devices and their fabrication method. The invention proposes a BAW device comprising at least a first BAW resonator and a second BAW resonator, which are acoustically coupled by using an acoustic coupling structure. In particular, the BAW device comprises a piezoelectric layer configured to propagate a BAW, a first bottom electrode and a second bottom electrode provided beneath the piezoelectric layer, respectively, and a first top electrode and a second top electrode provided on the piezoelectric layer, respectively. The first top electrode and the first bottom electrode sandwich the piezoelectric layer to form a first BAW resonator, the first BAW resonator comprising a first resonator region, which is a region of the piezoelectric layer located between the first top electrode and the first bottom electrode. The second top electrode and the second bottom electrode sandwich the piezoelectric layer to form a second BAW resonator, the second BAW resonator comprising a second resonator region, which is a region of the piezoelectric layer located between the second top electrode and the second bottom electrode. The BAW device further comprises an acoustic coupling structure arranged between the first top electrode and the second top electrode on the piezoelectric layer. The acoustic coupling structure is configured to allow an acoustic wave to propagate from the first resonator region into the second resonator region through the acoustic coupling structure. An optimization of lateral traveling waves enables an acoustic coupling of adjacent BAW resonators operating in their fundamental thickness-extensional (TE) mode or in a thickness-shear (TS) mode.