XBAR Resonator Gap Dielectric Stripes for Acoustic Leakage Control
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Solution Overview
Problem
Existing RF filters, including XBAR resonators, face issues with acoustic energy leakage and undesired ripples in resonator admittance, leading to increased insertion loss and poor performance at higher frequencies and bandwidths required for future communication networks.
Innovation Solution
Incorporation of gap dielectric stripes in busbar-electrode gaps within XBAR resonators to confine acoustic energy and move problematic gap mode spurs to less critical frequency ranges, reducing energy leakage and improving device Q.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional XBAR resonators are used without gap dielectric stripes, then the device structure is simpler, but acoustic energy leakage increases and insertion loss worsens
Solution Approach 1:
The busbar-electrode gap region is segmented by introducing dielectric stripes that divide the continuous gap into multiple sections. These stripes are positioned at specific locations within the gap to create acoustic confinement zones, thereby reducing energy leakage without requiring complete structural redesign
Solution Approach 2:
Dielectric stripes are introduced as intermediary elements within the busbar-electrode gap. These stripes act as acoustic barriers that mediate between the acoustic wave field and the gap region, reflecting acoustic energy back into the resonator and reducing leakage through the gap
2Reliability
If conventional XBAR resonators are used without gap dielectric stripes, then manufacturing is simpler, but gap mode spurs appear at critical frequencies
Solution Approach 1:
Rather than modifying the entire resonator structure, dielectric stripes are applied locally within the busbar-electrode gap regions. This localized approach targets the specific problem area (gap mode spurs) while maintaining the overall simplicity of the manufacturing process for the rest of the device
Solution Approach 2:
The dielectric stripes modify the local electromagnetic and acoustic parameters within the gap region. By changing the dielectric constant and acoustic impedance in these localized areas, the resonance characteristics are altered to suppress gap mode spurs without requiring fundamental changes to manufacturing parameters
3Loss of energy
If gap dielectric stripes are added to reduce acoustic energy leakage, then insertion loss improves, but device complexity increases
Solution Approach 1:
The resonator structure is segmented by adding dielectric stripes only in the critical busbar-electrode gap regions rather than throughout the entire device. This selective segmentation reduces acoustic energy leakage at the most problematic locations while minimizing the overall increase in structural complexity
Solution Approach 2:
The dielectric stripe pattern is copied and applied to multiple busbar-electrode gap regions in a standardized manner. This repetitive use of the same structural element across different locations achieves comprehensive acoustic confinement without requiring complex unique designs for each region
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 reduces acoustic energy leakage and lowers the amplitude of gap mode spurs, enhancing the performance of XBAR resonators by improving frequency confinement and reducing insertion loss.
Implementation Method 1
a piezoelectric plate attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity
Implementation Method 2
An interdigital transducer (IDT) on a surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm; a microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm
Implementation Method 3
Incorporation of gap dielectric stripes in busbar-electrode gaps within XBAR resonators to confine acoustic energy and move problematic gap mode spurs to less critical frequency ranges, reducing energy leakage and improving device Q
Implementation Method 4
a portion of the piezoelectric plate forming a diaphragm that spans a cavity in an intermediate dielectric layer of the substrate
Data Source
AI summary
An acoustic resonator device includes a substrate having a surface and a piezoelectric plate having front and back surfaces, with the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. Stripes of a dielectric material formed over the plate in gaps between ends of the interleaved fingers and opposing busbars of the IDT.