SAW Resonator IDT Pitch and Connection Layout for Spurious Emissions
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Solution Overview
Problem
Conventional surface acoustic wave (SAW) elements used in filters, particularly in ladder-type filters, experience undesirable spurious emissions due to non-periodicity caused by reversed electrode finger connections, which degrade the filter's performance and durability by concentrating power at certain frequencies.
Innovation Solution
The implementation of a SAW element with a piezoelectric substrate and an interdigital transducer (IDT) electrode featuring a combination of normal and reversed electrode finger connections, along with varying electrode finger pitches in different regions, to improve frequency response and suppress spurious emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reversed electrode finger connections are used in SAW elements, then frequency response characteristics are improved, but spurious emissions occur due to non-periodicity
Solution Approach 1:
The patent applies local quality by differentiating the connection pattern of electrode fingers in different regions of the IDT. Specifically, electrode fingers in a first region are connected to first busbar terminals, while electrode fingers in a second region are connected to second busbar terminals, creating region-specific connection characteristics that eliminate spurious emissions while maintaining improved frequency response.
2Ease of manufacture
If uniform electrode finger pitch is used, then manufacturing is simplified, but frequency response optimization is limited
Solution Approach 1:
The patent implements varying electrode finger pitch across different regions of the IDT. The first region has a first pitch between adjacent electrode fingers, while the second region has a second pitch that differs from the first pitch. This local differentiation optimizes frequency response characteristics for specific frequency ranges while remaining manufacturable.
3Power
If power is concentrated at certain frequencies, then resonance is enhanced, but durability decreases due to excessive power concentration
Solution Approach 1:
The patent changes the connection parameters of electrode fingers by dividing them into different regions with different connection patterns to busbar terminals. This parameter change distributes the power across multiple frequencies rather than concentrating it at a single resonant frequency, thereby enhancing durability while maintaining effective power utilization.
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 enhances the filter's frequency response characteristics while eliminating spurious emissions, leading to improved signal attenuation and increased durability by evenly distributing power across frequencies.
Implementation Method 1
an interdigital transducer (IDT) electrode formed on the piezoelectric substrate and configured to excite an acoustic wave
Implementation Method 2
a piezoelectric substrate and an interdigital transducer (IDT) electrode formed on the piezoelectric substrate and configured to excite an acoustic wave
Data Source
AI summary
A SAW element configured to suppress spurious emissions resulting from non-periodicity of an IDT electrode finger arrangement. In one example, the SAW element is a resonator comprising an IDT electrode including a first plurality of IDT electrode fingers connected to a first busbar and a second plurality of IDT electrode fingers connected to a second busbar, and reflectors having a plurality of reflector fingers. The pluralities of first and second IDT electrode fingers are alternatively connected to each busbar by either normal connections or reversed connections and include regions arranged by at least two different types of pitches. The normal connections are such that either the odd-numbered or even-numbered IDT electrode fingers connect to the first busbar, and the reversed connections are such that the opposite group of IDT electrode fingers connect to the first busbar.