Stepped Comb Capacitive Element for Spurious Resonance Suppression
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Solution Overview
Problem
Existing capacitive elements on piezoelectric substrates for acoustic wave devices suffer from spurious resonance issues, which affect the device's performance and efficiency.
Innovation Solution
A capacitive element design featuring interdigital comb electrodes with step portions on a piezoelectric substrate, where the electrode fingers are bent partway along their length, creating different phases for acoustic waves and suppressing resonance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional capacitive element with straight comb electrodes is used on a piezoelectric substrate, then the device size can be reduced, but spurious resonance occurs affecting device performance
Solution Approach 1:
The electrode fingers are bent partway along their length instead of being straight, creating a curved geometry that suppresses spurious resonance. The bending creates different phases for acoustic waves traveling through different portions of the electrode finger, which interferes destructively with spurious resonant modes while maintaining the compact capacitive structure.
2Device complexity
If straight comb electrodes are used in the capacitive element, then the structure is simple, but unwanted acoustic wave generation occurs
Solution Approach 1:
The electrode fingers incorporate bend portions that create phase differences in acoustic wave propagation. This curved geometry suppresses unwanted acoustic wave generation through destructive interference while adding minimal structural complexity to the otherwise simple comb electrode design.
3Ease of manufacture
If the capacitive element uses traditional parallel electrode fingers, then manufacturing is straightforward, but resonance characteristics are poor
Solution Approach 1:
The bent electrode finger design can be manufactured using standard photolithography and deposition processes, maintaining ease of fabrication. The bend portions are formed as continuous curved structures that are compatible with conventional thin-film deposition techniques, while significantly improving resonance characteristics by suppressing spurious modes.
Solution Approach 2:
The electrode finger geometry is modified by introducing bend portions with specific curvature radii and angles. These parameter changes optimize the phase distribution of acoustic waves to suppress resonance while maintaining manufacturability through controlled deposition thickness and pattern definition.
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 capacitive element effectively reduces spurious resonance across the capacitive part, enhancing the frequency characteristics and reducing unwanted acoustic wave generation, thereby improving the overall performance of the acoustic wave device.
Implementation Method 1
a capacitive element is also provided on a piezoelectric substrate
Implementation Method 2
the electrode fingers are bent partway along their length, creating different phases for acoustic waves and suppressing resonance characteristics
Data Source
AI summary
A capacitive element includes a piezoelectric substrate, a first electrode finger extending towards a positive side in a first direction, and a second electrode finger disposed facing and spaced apart from the first electrode finger in a second direction intersecting the first direction, extending towards a negative side in the first direction, and connected to a different potential from the first electrode finger. The first electrode finger includes a first portion extending in the first direction and a second portion extending from the first portion, through a first step portion, and at a different position in the second direction from the first portion. The second electrode finger includes a third portion disposed facing the second portion and extending in the first direction, and a fourth portion extending from the third portion through a second step portion, extending from the second portion in the first direction, and facing the first portion.