Acoustic Wave Resonator Gap Spacing for Q Value and Suppression
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Solution Overview
Problem
Filters and duplexers in mobile phones face a trade-off between low insertion loss and high suppression characteristics, where reducing passband loss deteriorates suppression outside the passband, making it difficult to improve signal/noise ratio and communication quality.
Innovation Solution
A resonator design with comb-shaped electrodes on a piezoelectric substrate, where the distance between gaps (ΔD) is 0.5λ or greater, improving the Q value and reducing Rayleigh wave scattering, thereby enhancing both passband loss and suppression characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the loss in the passband is designed to be small, then the suppression outside the passband deteriorates
Solution Approach 1:
The patent applies local quality by creating different gap configurations in different regions of the IDT. Specifically, first gaps are formed between electrode fingers and second gaps are formed between dummy electrode fingers, with different spacing relationships (ΔD ≥ 0.5λ for at least two adjoining gaps). This local differentiation allows the resonator to achieve both low passband loss and high suppression characteristics simultaneously by optimizing each region's contribution to the overall frequency response.
2Loss of energy
If the Q value of the resonator is improved to reduce passband loss, then the suppression outside the passband deteriorates
Solution Approach 1:
The patent employs parameter changes by systematically varying the gap distances (ΔD) between electrode structures. By setting ΔD ≥ 0.5λ for at least two adjoining gaps among the first and second gaps, the resonator achieves an optimized Q value that simultaneously improves passband characteristics and maintains stopband suppression. This parameter optimization allows the resonator to achieve both low insertion loss and high rejection ratio.
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 resonator design achieves a higher Q value and reduced loss in the passband while maintaining or improving suppression outside the passband, leading to improved signal quality and communication efficiency in mobile phone filters and duplexers.
Implementation Method 1
a first comb-shaped electrode formed on a piezoelectric substrate
Implementation Method 2
Surface acoustic wave resonators, boundary acoustic wave resonators, and Love wave resonators including an IDT (Interdigital Transducer) have been used as the acoustic wave resonator
Implementation Method 3
A Rayleigh wave scattering in a surface acoustic wave resonator is described in IEEE Trans. Ultrason. Ferroelect., Freq. Contr., Vol. 48, no. 6, pp. 1517-1526, 2001
Data Source
AI summary
A resonator includes: a first comb-shaped electrode including a first bus bar, first electrode fingers coupled to the first bus bar and extending in an extension direction, and first dummy electrode fingers coupled to the first bus bar; and a second comb-shaped electrode including a second bus bar, second electrode fingers coupled to the second bus bar, extending in the extension direction, and facing the first dummy electrode fingers through first gaps, and second dummy electrode fingers coupled to the second bus bar and facing the first electrode fingers through second gaps, wherein 0.5λ≦ΔD where ΔD represents a distance in the extension direction between at least two gaps that are at least adjoining two of the first gaps or/and at least adjoining two of the second gaps, and λ represents pitches of the first electrode finger and the second electrode finger.