Bent Ladder SAW Filter Layout to Reduce Terminal Interference
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Solution Overview
Problem
Existing elastic wave filters with ladder-form configurations face challenges in reducing interference between input and output terminals and improving power durability, especially in wireless communication applications, due to overlapping resonators and inefficient signal propagation.
Innovation Solution
The elastic wave filter incorporates a series arm with split arms and parallel resonators connected in a ladder form on a piezoelectric substrate, where the series arm is bent to reduce terminal interference and power durability is enhanced by splitting resonators, preventing overlap between resonators closest to the input and output terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If resonators are arranged in a straight ladder form, then the filter structure is simple, but terminal interference increases and power durability decreases
Solution Approach 1:
The series arm is segmented into first and second split arms that are bent relative to each other, creating a non-linear arrangement of resonators. This segmentation allows the filter to maintain structural simplicity while reducing terminal interference and improving power durability through the bent configuration.
Solution Approach 2:
The series arm transitions from a one-dimensional straight line arrangement to a two-dimensional bent configuration. By extending the series arm in a bent manner rather than a straight line, the patent achieves reduced terminal interference and improved power durability while maintaining structural simplicity.
2Area of stationary object
If resonators are arranged in a straight line, then the layout is compact, but overlapping between input and output resonators occurs causing interference
Solution Approach 1:
The series arm is extended in a bent configuration rather than a straight line, utilizing two-dimensional space more effectively. This allows the filter to maintain a compact overall layout while preventing overlapping between input and output resonators, thereby reducing terminal interference.
3Object-generated harmful factors
If the series arm is bent into split arms, then terminal interference is reduced, but the device complexity increases
Solution Approach 1:
The series arm is divided into first and second split arms that are bent relative to each other. This segmentation approach reduces terminal interference by separating the input and output resonators, while the modular nature of the segmentation keeps the increased complexity manageable and systematic.
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 reduces terminal interference, enhances power durability, and improves electric characteristics by preventing resonator overlap, resulting in a more efficient SAW filter with improved attenuation characteristics and reduced spurious emission.
Implementation Method 1
a piezoelectric substrate, a first terminal, a second terminal, and a filter body. The filter body is located on the piezoelectric substrate
Implementation Method 2
The elastic wave is, for example, a surface acoustic wave (SAW)
Data Source
AI summary
A filter body has a series arm including a plurality of series resonators connected in series with one another and one or more parallel resonators in such a manner that the series arm and the parallel resonators are connected in a ladder form. The series arm has a bent part, and when viewed from an elastic wave propagation direction, a series resonator located closest to a first terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the first terminal from a circuit perspective among the plurality of parallel resonators do not overlap a series resonator located closest to a second terminal from a circuit perspective among the plurality of series resonators and a parallel resonator located closest to the second terminal from a circuit perspective among the plurality of parallel resonators.