Apodized Elastic Wave Resonator Layout for Lower Insertion Loss
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Solution Overview
Problem
Existing elastic wave resonators and ladder filters face issues with unsatisfactory Q value at resonant frequency and high insertion loss, despite increased electric power handling capability, due to large non-crossing regions and resistive loss in dummy electrode fingers.
Innovation Solution
An elastic wave resonator with apodization-weighted IDT electrodes, featuring high metallization ratios in non-crossing regions and diamond-shaped weighting, reduces resistive loss and insertion loss while maintaining high electric power handling capability by optimizing electrode finger widths and common electrode extensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If apodization weighting is applied with large non-crossing regions in the IDT electrode, then electric power handling capability is increased, but Q value at resonant frequency becomes unsatisfactory due to reduced excitation intensity and increased resistive loss
Solution Approach 1:
The patent applies different metallization ratios to different regions of the IDT electrode. Specifically, the crossing region has a first metallization ratio optimized for excitation intensity, while the non-crossing region has a second metallization ratio that is higher than the first. This local differentiation allows the non-crossing region to contribute more to power handling while the crossing region maintains sufficient excitation intensity for acceptable Q value.
2Object-affected harmful factors
If the crossing width of IDT electrode is reduced in non-crossing regions, then spurious due to transverse-mode ripples is reduced, but resistive loss of dummy electrode fingers increases
Solution Approach 1:
The patent changes the metallization ratio parameter in the non-crossing region to be higher than in the crossing region. This parameter change increases the conductivity of the dummy electrode fingers in the non-crossing region, thereby reducing resistive loss while maintaining the reduced crossing width that suppresses transverse-mode ripples.
3Reliability
If metallization ratio is increased in non-crossing region, then resistive loss is reduced and Q value is improved, but device complexity increases due to varying electrode dimensions
Solution Approach 1:
The patent implements local quality by making the electrode fingers in the non-crossing region wider than those in the crossing region, creating distinct zones with different metallization ratios. This localized structural differentiation improves Q value by reducing resistive loss in the non-crossing region while keeping the overall device complexity manageable through a systematic design approach.
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 achieves a high Q value, reduced insertion loss, and enhanced electric power handling capability, making it suitable for use in duplexers and band-pass filters, particularly in UMTS Band 2 transmission-side applications.
Implementation Method 1
an IDT electrode 7 located on a piezoelectric substrate 6
Data Source
AI summary
An acoustic wave resonator that is excellent in terms of return loss characteristics at the resonant and anti-resonant frequencies and that is capable of effectively reducing loss includes an IDT electrode in which a plurality of first electrode fingers and a plurality of second dummy electrode fingers are connected to a first common electrode, a plurality of second electrode fingers and a plurality of first dummy electrode fingers are connected to a second common electrode. Apodization weighting is applied in the acoustic wave propagation direction. The metallization ratio of a non-crossing region is relatively high compared with the metallization ratio of a crossing region in the acoustic wave propagation direction.