Surface Acoustic Wave Filter Layout Using Cover-Side Cancel Circuit
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Solution Overview
Problem
The existing surface acoustic wave devices face challenges in miniaturization due to the requirement of additional surface area for additional circuits, which can lead to increased device size and intersecting wiring patterns on the piezoelectric substrate, limiting design freedom.
Innovation Solution
The surface acoustic wave device incorporates a cancel circuit connected in parallel to the filter, with a portion of the wiring pattern placed on a cover portion opposing the piezoelectric substrate, reducing the space needed on the substrate and eliminating wiring pattern intersections, thereby maintaining device size and enhancing design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional circuit is added in parallel to the filter to ensure attenuation amount in the blocking band, then the attenuation characteristics are improved, but the device size increases or wiring patterns intersect on the piezoelectric substrate
Solution Approach 1:
The patent applies dimensionality change by moving the wiring pattern from the two-dimensional plane of the piezoelectric substrate to the three-dimensional space of the cover portion. Specifically, the wiring pattern is arranged on the back surface of the cover portion (opposite to the piezoelectric substrate), utilizing the Z-axis dimension to eliminate spatial conflict and prevent wiring intersections while maintaining compact device size.
Solution Approach 2:
The patent implements nesting by integrating the additional circuit within the existing device structure. The cancel circuit is positioned inside the cover portion, nested within the overall device housing, which allows the additional functionality to be accommodated without increasing the external device dimensions.
2Reliability
If an additional circuit is added in parallel to the filter to ensure attenuation amount in the blocking band, then the attenuation characteristics are improved, but wiring patterns intersect on the piezoelectric substrate
Solution Approach 1:
The patent resolves wiring pattern intersections by transitioning from two-dimensional wiring layout on the substrate to three-dimensional wiring arrangement on the cover portion. The wiring pattern is placed on the back surface of the cover portion, utilizing the vertical dimension to completely avoid intersections with substrate-level wiring patterns, thereby simplifying the overall wiring design.
3Ease of manufacture
If wiring patterns are arranged on the piezoelectric substrate to connect functional elements, then electrical connections are established, but device size increases when additional circuits are included
Solution Approach 1:
The patent relocates the wiring pattern from the piezoelectric substrate plane to the cover portion's back surface, utilizing the third dimension (depth/thickness) to separate wiring layers. This spatial separation allows electrical connections to be maintained while preventing wiring patterns from occupying additional substrate area, thus avoiding device size increase.
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
This configuration improves attenuation characteristics in the blocking band while preventing device size increase and enhancing design freedom by relocating wiring patterns to the cover portion, thus optimizing the use of substrate space.
Implementation Method 1
a surface acoustic wave resonator is defined by the piezoelectric substrate and the IDT electrode
Implementation Method 2
a vibration space between a piezoelectric substrate and a cover portion opposing the piezoelectric substrate
Data Source
AI summary
A surface acoustic wave device includes a piezoelectric substrate, functional elements on the piezoelectric substrate, a cover portion that opposes the piezoelectric substrate with a support layer interposed therebetween, and an input/output terminal on the cover portion. At least a portion of the functional elements includes an interdigital transducer electrode, and a surface acoustic wave resonator is defined by the piezoelectric substrate and the IDT electrode. The functional elements include a filter that passes a signal in a predetermined frequency band, and a cancel circuit which is connected in parallel to the filter and attenuates a signal outside the predetermined frequency band in signals output from the output terminal. A portion of a wiring pattern connecting a first functional element and a second functional element included in the plurality of functional elements is provided on the cover portion.