Elastic Wave Resonator Pitch Layout for Spurious Signal Suppression
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Solution Overview
Problem
Existing elastic wave filters generate spurious signals at frequencies different from the resonant frequency of the main resonance.
Innovation Solution
An elastic wave resonator with a piezoelectric body and electrode fingers arranged in specific regions, where the electrode finger groups have different pitches and duty ratios to cancel out the effects on higher and lower resonant frequencies, maintaining uniformity of the resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode fingers with uniform pitch are used in the entire resonator, then the resonant frequency is uniform, but spurious signals are generated at frequencies different from the main resonant frequency
Solution Approach 1:
The electrode finger array is segmented into multiple groups with different pitches. Specifically, a first group of electrode fingers has a first pitch, while a second group of electrode fingers has a second pitch different from the first pitch. This segmentation allows different pitch regions to generate different resonant frequencies, thereby suppressing spurious signals while maintaining the main resonant frequency uniformity through careful design of the pitch distribution and duty ratios.
Solution Approach 2:
Different regions of the electrode finger array are assigned different local characteristics (different pitches and duty ratios). The first region contains electrode fingers with a first pitch and the second region contains electrode fingers with a second pitch. This local quality variation enables selective suppression of spurious signals at specific frequency ranges while preserving the desired resonant frequency characteristics in the main operating band.
2Object-generated harmful factors
If different pitch electrode finger groups are used, then spurious signal strength is reduced, but frequency uniformity across the resonator is compromised
Solution Approach 1:
The pitch parameter of the electrode fingers is changed across different groups to suppress spurious signals. By adjusting the pitch of electrode finger groups in different regions, the resonant frequencies of these regions are shifted away from the main resonant frequency, thereby reducing spurious signal generation. The parameter changes are carefully controlled to maintain overall frequency uniformity in the desired operating range.
Solution Approach 2:
The electrode finger array employs asymmetric pitch distribution rather than uniform pitch throughout. The first group of electrode fingers has a different pitch from the second group, creating an asymmetric structure that selectively suppresses spurious signals. This asymmetry is designed to create frequency separation between the main resonant mode and spurious modes while maintaining the desired resonant frequency uniformity through complementary duty ratio adjustments.
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
Reduces the strength of spurious signals while maintaining the uniformity of resonant frequency, improving the characteristics of the elastic wave resonator.
Implementation Method 1
a piezoelectric body (6), and a plurality of electrode fingers (14) located on the piezoelectric body (6)
Implementation Method 2
a spurious signal that oscillates at a frequency different from a resonant frequency of the main resonance is generated
Data Source
AI summary
The strength of a spurious signal is reduced while maintaining the uniformity of a resonant frequency in an identical elastic wave resonator. An elastic wave resonator (4) includes a piezoelectric body (6), and a plurality of electrode fingers (14, 22) located on the piezoelectric body and arranged in a propagation direction (TD) of an elastic wave. A region in which the plurality of electrode fingers are located includes a first region (24A) and a second region (24B) in a plan view. The plurality of electrode fingers include a first electrode finger group (14A) located in the first region and a second electrode finger group (14B) located in the second region, and a pitch (PA) of the first electrode finger group is different from a pitch (PB) of the second electrode finger group. The first region and the second region have frequency effective-characteristics acting in a direction to cancel out effects on a higher resonant or antiresonant frequency and a lower resonant or antiresonant frequency brought about by a magnitude correlation between the pitches of the first and second electrode finger groups.