Mixed-Thickness IDT Layout for Spur-Controlled Bulk Acoustic Resonators
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Solution Overview
Problem
Existing RF filters face challenges in achieving improved power handling performance while mitigating spurs in the filter passband, particularly as the demand for higher frequency operation increases.
Innovation Solution
Implementing a mixed thin-thick IDT configuration in bulk acoustic resonators, where a combination of thin and thick IDT fingers are used, with specific pitch and thickness variations to achieve a single resonance frequency, enhancing power handling without introducing significant spurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If thinner IDT fingers are used to mitigate spurs in the filter passband, then spur reduction is improved, but power handling capability deteriorates
Solution Approach 1:
The IDT structure is divided into different regions with different finger thicknesses. The first IDT has thinner fingers optimized for spur reduction, while the second IDT has thicker fingers optimized for power handling. This local differentiation allows each region to perform its specific function optimally without compromising the other.
Solution Approach 2:
The IDT is segmented into multiple independent IDT structures (first IDT and second IDT) with different characteristics. Each IDT can be independently designed and optimized for specific requirements, allowing the system to achieve both spur mitigation and high power handling capability simultaneously.
2Power
If thicker IDT fingers are used to improve power handling capability, then power handling is improved, but spurs in the filter passband increase
Solution Approach 1:
Different regions of the IDT structure are assigned different finger thicknesses based on their functional requirements. The second IDT with thicker fingers handles power processing, while the first IDT with thinner fingers manages frequency selectivity with reduced spurs.
Solution Approach 2:
The IDT is divided into separate first IDT and second IDT structures that can be independently optimized. This segmentation allows the thicker-fingered second IDT to handle power requirements without the negative spur effects that would occur if the entire IDT used thick fingers.
3Power
If a mixed thin-thick IDT configuration is used to improve power handling without spurs, then power handling and spur reduction are improved, but device complexity increases
Solution Approach 1:
Multiple IDT structures with different characteristics are merged into a single integrated resonator device. The first IDT and second IDT work together in a unified structure, achieving both spur reduction and power handling improvement without requiring separate devices.
Solution Approach 2:
The mixed thin-thick IDT configuration provides multi-functionality within a single device structure. It simultaneously achieves frequency filtering, spur mitigation, and high power handling capability, eliminating the need for multiple separate components.
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 mixed thin-thick IDT configuration improves power handling capability and reduces spurs, enabling better performance in high-frequency RF filters.
Implementation Method 1
A bulk acoustic resonator includes a piezoelectric layer; and an interdigital transducer (IDT) over a surface of the piezoelectric layer
Implementation Method 2
an interdigital transducer (IDT) over a surface of the piezoelectric layer
Implementation Method 3
Bulk acoustic resonator with varying thickness IDT configuration
Data Source
AI summary
A bulk acoustic resonator, a filter device including the bulk acoustic resonator, and a radio frequency module including the filter device are provided. The bulk acoustic resonator includes a piezoelectric layer; and an IDT over a surface of the piezoelectric layer. The IDT includes first and second pluralities of interleaved fingers. A pair of subsections of the second plurality of interleaved fingers are disposed on opposing sides of the first plurality of interleaved fingers in a lengthwise direction of the IDT. A first thickness of the first plurality of interleaved fingers is different from a second thickness of the second plurality of interleaved fingers. Moreover, a first pitch of the first plurality of interleaved fingers is different from a second pitch of the second plurality of interleaved fingers.