DMS SAW Filter IDT Layout for Adjacent-Band Attenuation
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Solution Overview
Problem
Conventional double mode surface acoustic wave (DMS) filters face challenges in increasing attenuation in the attenuation band adjacent to the wide band side for the passband while maintaining a compact product size, as existing methods require additional space and wiring for capacitance connections.
Innovation Solution
The DMS filter design incorporates interdigital transducers with specific configurations of Type 1 and Type 2 electrode fingers on a piezoelectric substrate, allowing for controlled capacitance formation between adjacent transducers without external capacitance components, thereby enhancing attenuation and miniaturizing the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external capacitance components and wiring are added to improve attenuation in the attenuation band, then attenuation performance is improved, but product size increases
Solution Approach 1:
The patent merges the capacitance function with the IDT structure by making electrode fingers of adjacent IDTs overlap and face each other. This integration eliminates the need for separate external capacitance components and their connecting wiring, thereby improving attenuation performance while avoiding increase in product size. The capacitance is formed in-situ between the facing electrode fingers of adjacent IDTs.
2Reliability
If the number of electrode fingers is increased to improve attenuation, then attenuation performance is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by making only specific electrode fingers (one Type 1 and one Type 2 from adjacent IDTs) overlap and face each other to form capacitance, while other electrode fingers maintain their conventional non-overlapping arrangement. This selective local modification achieves the desired attenuation improvement without requiring complete redesign of the entire electrode structure, thus limiting the increase in device complexity.
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 effectively increases attenuation in the desired frequency band while reducing the product size by integrating capacitance within the filter structure, improving performance and space efficiency.
Implementation Method 1
a piezoelectric substrate
Implementation Method 2
interdigital transducers (IDTs)... formed on a piezoelectric substrate
Implementation Method 3
double mode surface acoustic wave (SAW) filter
Data Source
AI summary
A double mode SAW (DMS) filter includes: a plurality of interdigital transducers (IDTs), each having a plurality of Type 1 electrode fingers and a plurality of Type 2 electrode fingers formed on a piezoelectric substrate, wherein one Type 2 electrode finger among the plurality of Type 2 electrode fingers is disposed between two adjacent Type 1 electrode fingers among the plurality of Type 1 electrode fingers, and in a first IDT and a second IDT included in the plurality of IDTs to be adjacent to each other, one Type 1 electrode finger of the second IDT is disposed between two Type 1 electrode fingers of the first IDT. Accordingly, it is possible to provide a DMS filter capable of improving the amount of attenuation in an attenuation band adjacent to the wide band side for the passband and miniaturizing a product by saving space.